It is known to determine the chemical composition of a sample with the aid of infrared analysis, whereby infrared light is either reflected against a sample or is allowed to penetrate through a sample. By measuring the amount of energy absorbed by the sample at certain wave lengths, it is possible to determine the chemical composition of the product. This is utilized in a variety of different contexts, inter alia in the food industry, for product analysis.
In the flour milling industry, it has been the practice for many years to check the flour quality with the aid of infrared analysis as described above, and in this case reflection analysis has been used, i.e. reflected light from the sample has been measured.
It has, however, been a long felt need to be able to perform effective and rapid analysis of unmilled grain, for the purpose of better quality sorting of different shipments of grain. Tests have shown that equipment which has, up to now, usually been used for reflection analysis of flour, and in which light detectors of lead sulphide type have been used, has not been usable for whole grain analysis, since the signals obtained have proved to be too small in order to be of any practical use. It has instead been suggested to perform whole grain analysis by transmission measurement of wave lengths of less than 1100 nm and using light detectors of silicon type, see for example U.S. Pat. No. 4,286,237. One disadvantage is, however, that analysis can only be performed on relatively thin layers of grain, where the thickness does not exceed 25 or 30 mm. It is also proved difficult to perform analysis on samples which are in motion relative to the analysis equipment, i.e. to measure a continuous flow of grain. Another disadvantage is that any variations between a number of light sources used will affect the measurements negatively.